The present invention relates to a power transmission system for a vehicle of the type in which front and rear wheels are driven by the same engine.
Heretofore, various front drive base (FF base) vehicles have been developed in which a driving connection to rear wheels can be attained by coupling of a hydraulic clutch. And for operating the clutch, an oil pump is provided separately (e.g. a motor-driven oil pump or an oil pump for an automatic transmission), and the discharge pressure of the oil pump is adjusted suitably and then fed to the clutch to control the transmission of driving force to the rear wheels.
In such conventional power transmission system for vehicle, however, it is necessary to provide an oil pump separately, and therefore the means for adjusting the discharge pressure of the oil pump becomes complicated in structure.